There's continuing debate over whether the Great Lakes are losing water.
This weekend, Traverse City will host a conference on Saving the Great Lakes.
It will feature an international speaker who says, without stronger protections, demand for fresh water in coming decades may leave the lakes "bone dry".
Scientists who study the lakes say that claim is misleading.
Canadian "Ralph Nader"
Maude Barlow is sometimes described as the "Canadian Ralph Nader" when it comes to protecting fresh water.
She chairs a citizen activist group called the Council of Canadians.
She says there's a misconception that water in the Great Lakes replenishes itself every year with rainfall.
Barlow says a significant amount of the water is consumed every day, to grow and process food for example.
"And I think you'll find a lot of this water is actually leaving the Great Lakes Basin in the form of industrial products that get exported, in the form of commodity products that get exported, in the form of bottled water, in the form of diversions that don't come back."
Pumping Too Much?
In her new report Barlow looks at recent scientific studies of the Great Lakes.
She says the amount of fresh water pumped out of the ground to meet human needs is a growing concern.
For instance, she says deep wells in the Chicago area reach as far underground as the city's tallest skyscrapers.
And Barlow says a study shows those wells are capturing groundwater that ordinarily flows into Lake Michigan.
In fact the wells are pumping so hard they're beginning to pull water from the bottom of the lake.
Barlow says that worldwide thirsty countries are extracting groundwater at a rapidly increasing rate.
She highlights research that predicts in twenty years demand for fresh water will outstrip supply.
And she takes that to be a warning for the Great Lakes.
"If we are pumping the water and the groundwater of the Great Lakes as fast as groundwater is being pumped around the world the Great Lakes could be bone dry in 80 years. Now they're not saying they will be but they're saying if the extraction rate around the Great Lakes is as great as the global extraction rate, we're in trouble."
Scientists Disagree with Report
Barlow doesn't know exactly how much water is being removed from the Lakes.
But she's concerned that scientists don't have a good handle on it either.
Jim Nicholas is with the U.S. Geological Survey.
He says scientists do know that all of the withdrawals for human use in the entire Great Lakes Basin are dwarfed by the amounts that cycle through the system from rainfall, evaporation and rivers flowing into the lakes.
"The water's replenished every year on about the same amount that it leaves the watershed. That's why the water levels in the great lakes pretty much fluctuate around some mean or average water level since historical times."
Nicholas says Barlow's paper is misleading.
The U.S.G.S. did the study of groundwater in the Chicago area.
And he says the amount of water that is being drawn from Lake Michigan by the pumps there essentially is a slow trickle.
In contrast, Nicholas says, there are some fairly large diversions of water both into and out of the Great Lakes.
For instance, the Chicago Diversion pulls a river of water away from Lake Michigan every day for the city's wastewater treatment.
Nicholas says that only lowers the lake level by a little more than a couple of inches.
And he says that amount is more than offset by giant diversions of water into the Great Lakes system from rivers in the far north of Canada.
"The diversions into the Great Lakes at Lake Superior raise the lake levels on Michigan and Huron by about five inches. So, really if you look at diversions, it's a positive number not a negative number."
Small Net Loss
Jim Nicholas says overall there is a net loss from the system when you consider all human consumption of water.
But he says it's a tiny fraction, less than one percent, of the amount that flows through the cycle from all sources every year.
So Nicholas says it's very unlikely that such a water-rich region will ever be pumped "bone dry" as Barlow suggests may happen.
But Maude Barlow is convinced that demands on Great Lakes water will slowly deplete the supply.
And in her paper she calls for a moratorium on any new groundwater pumping in the region until more studies are done.
"Collectively we're losing a lot of water from the Great Lakes every year. The work that I've done here frankly skims the surface. What we need is to get some scientists really looking at this issue in a much deeper way and asking the question about where has the water from the Great Lakes gone."
Maude Barlow will give a keynote speech at the State Theater in Traverse City Friday evening to kick off the "Saving the Great Lakes Forever" conference.
Bob Allen, Interlochen Public Radio